Michelle Collins lives with her husband Matt and daughters, Jacqueline age 11 and Michaela age 6, in Westchester County, NY. She is certified as an American Council on Exercise (ACE) personal fitness trainer and owner of Fit and Happier, a fitness service specializing in one-on-one and small-group home-based training for women. Learn more at www.fitandhappier.com or find a certified fitness professional near you at www.acefitness.org and enter your zip code under ACE GetFit.

Dear Jacqueline and Michaela,

You may wonder why I walk in the pouring rain to the point where my socks and sneakers grow to twice the weight they were when I left the house. You may wonder, too, why I don well-treaded hiking boots to safely maneuver freshly fallen snow. You may even wonder why I ask you to busy yourselves quietly for an hour while unfamiliar women come to the house to be taught “how to exercise.”

Well, it may surprise you to learn that my behavior has nothing to do with the pursuit of an ideal body type, an addiction to exercise or a super-competitive spirit within me. The truth is, I’m driven by a much healthier goal. But to understand that you need to know a little more about our family — and our nation’s history. So here goes.

My Mom, your Memere, was born in 1934, in the midst of the Great Depression, and raised during World War II, when scarcity and back-breaking labor were the norm. As the country recovered, great advances were made and prosperity returned. Thanks to everything from the combustible engine and assembly-line manufacturing to more efficient heavy farm equipment and the interstate highway system — farmers could plant and harvest more crops with less manpower and food could be transported relatively easily and quickly. That meant affordable food was abundantly available to the average family.

Unlike today, women were expected primarily to tend to their homes. It was considered unladylike to play sports or even to sweat. Eventually, a cultural revolution would liberate women from this single-minded expectation, enabling them to compete in the workplace, even in careers that men once dominated. But that revolution happened long after Memere married and had three children in rural Massachusetts.

My father, a k a Pepere, needed our one car to drive to and from his job. That ruled out working outside the home for Memere. She focused on the one job she could have: becoming a mother (at which she happened to be awesome, by the way) and keeping a clean, orderly home. By today’s standards, she worked physically hard to do this job well.

Then, emerging as if overnight, along came cheaper home appliances and inexpensive, highly processed foods. As a result, she was able to get a lot of household chores done in a fraction of the time and effort that it had taken her mother. Now faced with a novel concept — downtime or leisure — she picked up sewing. It was a thrifty hobby, certainly worth doing, and she was great at it. But it’s also a highly sedentary hobby. Over time, like many in her generation, she ate more and moved less.

On top of that, almost everything she did, including her sewing, she did for others. She constantly mended our school clothes and my dad’s work clothes. She made dresses for me, quilts for baby gifts, even outfits for my Barbie dolls. She also crafted items to donate to school and church fundraisers. Only rarely would she make clothes for herself.

And so it was that as my Mom entered her 40s and then her 50s, she gained weight.